The transit agency tweeted there was a 20-minute delay systemwide during the early evening commute due to "extreme weather related trackway equipment problems." About 30 minutes later, BART sent a follow-up tweet indicating the problem had worsened to a "major delay systemwide."

Caltrain also enforced speed limits of 60 mph on all tracks from San Francisco to San Jose, due to the "potential of heat-induced expansion of tracks."

BART explained to Twitter followers that slowing down trains is a common precaution among rail systems worldwide during times of extreme heat. High temperatures can cause metal rails to contort into unnatural positions.

That being said, the agency said they're working on installing new equipment that can better withstand the heat.

"New rail and trackway equipment -- which are being installed piecemeal across the system thanks to Measure RR -- should be able to withstand heat better, partly by the simple fact that they are new and without the wear and tear," tweeted BART's official account.

San Francisco broke a same-day record Monday with a recorded temperature of 95 degrees, while other parts of the Bay Area easily soared above 100. While Tuesday's weather should be a bit cooler, significant drop in temperatures isn't forecast for the region until Wednesday.

P.S. If you're suffering on a slow-moving BART train with no air conditioning, try moving to another train car. Air conditioning is controlled on a car-by-car basis on BART, so don't sweat and suffer in silence if your car's AC is out. Try to find relief on the next car over.